1. Field of the Invention
The present invention relates to an image forming apparatus such as a digital copying machine.
2. Description of the Prior Art
In a digital copying machine, a document image is read by a sensor and is stored in a memory. Then, the image data stored in the memory can be processed in various ways. For example, a plurality of the same document image can be reproduced by reading the image data iteratively. It is possible to scale up and down the document image by processing the image data. It is also possible to rotate the document image. Then, a digital copying machine has various modes.
For example, a margin can be set for providing a margin at a specified position on a copy paper (refer for example Japanese Patent laid open Publication 54-74441/1979). A margin may be provided, for example, at a top side and at a left side of document images. Usually, a user can specify a margin position by using an operational panel.
The position of margin depends on a type of document such as a portrait document or a landscape document. A landscape document has an image which a person can observe normally if it is placed with its longer side before the person. On the other hand, a portrait document has an image which a person can see normally if it is placed with its shorter side before the person. Usually, a person accesses a copying machine before a longer side of a platen thereof, and an automatic document feeder placed above the platen has its longer side before the person.
Then, it is possible for a user to place portrait and landscape documents at specified image positions. For example, if a document is placed onto the platen with its longitudinal direction in parallel to the document feed direction, the document is assumed to be a portrait document, while if a document is placed onto the platen with its longitudinal direction perpendicular to the document feed direction, the document is assumed to be a landscape document. Then, a margin is set at a position specified by a user for example at a top position.
An N-in-1 mode is also known that a synthesized image of a plurality of documents with a number of N is formed on a single sheet of paper (refer to for example U.S. Pat. No. 4,912,518). For example, in 4-in-1 mode, four document images are synthesized on a sheet of paper. Usually, the arrangement of four landscape documents in a synthesized image depends on the document type, that is, landscape and portrait. If the document type can be determined according to the document direction on the platen as explained above, it is possible that a plurality of document pages can be synthesized correctly in a single sheet of paper according to the document direction on the platen.
However, it is not possible for a copying machine to set documents of all sizes on the platen along the two directions. For example, if a document size is the largest size say A3 which can be dealt by a copying machine, documents of A3 and B4 sizes can be set only with their longitudinal direction in parallel to the document feed direction. That is, a document occupying more than a half of image read area in the platen can be placed only along a specified direction. On the other hand, if the smallest size of document which can be fed by an automatic document feeder is A5 size, an A5 document can be fed onto the platen only along a longitudinal direction of the document because an A5 size document cannot be carried normally by rollers when it is fed. In such cases, the position of margins may not be set correctly according to the document type and document direction on the platen. Further, a plurality of pages may not be synthesized correctly on a sheet of paper in N-in-1 mode.